Japanese firm’s Vision Fund is amping up its bet on real estate

SoftBank Group Corp. is raising its bet on the real-estate sector, as the Japanese conglomerate’s tech-focused Vision Fund has invested $400 million in online homebuying marketplace Opendoor Labs Inc., the companies said Thursday.

The investment comes only three months after Opendoor said it raised $325 million to back its business of buying and selling houses exclusively online. SoftBank is valuing the San Francisco-based company at more than $2 billion, although some of the money will be used to buy shares from existing...